Charge calculator



Jan. '3, 1933. c. H. wARD 1893009 I `CHRGE CALCULATOR Filed sept. 21.1929 2 Sheets-Sheet 2 Patented Jan. 3, 1933 UNITED sTATEs PATENT oFFlcaCLEMSON H. WARD, OF BETELEHEM, PENNSYLVANIA, .ASSIGNOR T0 BETHLEH'EM'.STEEL COMPANY, A CORPORATION OF PENNSYLVANIA GHARGE cALcULA'roB.

Application filed September 21, 1929. Serial No. 394,167.

This invention relates to calculating instruments in which variousquantities may be represented numerically by proportionate values ofelectrical current, resistance and voltage and in which means areprovided for Operating upon the quantities numerically by suitablycombining the correspondmg electrical values in accordance with Ohms lawand other well known electrical principles; the desired results beingobtained from electrical measurementsof the combinations. For example,if it is desired to multiply factor X by factor Y to obtain product Z,factor X may be represented by a resistance of KX ohms, (K being anyconvenient constant) Y is then represented by a current thru resistanceX of KY amperes, whereupon Z will be indicated by a potential of KZvolts across the resistance. It is obviously immaterial which two ofthese factors are known and hence both multiplication and division canbe carried out on the basis of the same electrical relation. Additionmay be accomplished by putting representative resistances or voltages inseries and measuring. their totals. When voltages are used in thismanner the algebraic sum is obtained and subtraction is thereforepossible by reversing the polarity of any desired voltage.

My invention is of greatest value in rapidly solving problems involvingtwo or more mathematical Operations on a number ofquantities-particularly where compound factors are involved such as inthe solution of simultaneous equations. Such a problem is illustrated bythe calculation of the quantities of various materials required to makeup a furnace charge of given composition. In this case the compoundfactors are the sums of percentages of chemical elements in eachmaterial and in the composition desired. Each of these is multiplied bya factor representing the quantity of the material in question or of thedesired mixture. The accurate solution of such a problem involves thesolution of as many simultaneous equations as there are materials to beused. When this number exceeds five or six and the materials are ofcomplex analysis, it becomes impractical to solve the equations andmethods of approximation have heretofore been used.

In order to clearly illustratethe principle of the apparatus and itsmethod of operation, the following description will be limited to thecalculation of furnace charges but it is obvious that the apparatus maybe used to advantage in other calculations with or without suitablemodifications in the range of the instruments and in the switchingequipment used to connect them.

In the drawings, Fig. 1 shows an assembly of apparatus by which theprinciples of operation may be illustrated. Fig. 2 shows a simplifiedform of commercial calculator in which the essential switching andmeasuring instruments are included.

Referring to Fig. 1, A0, A'm and Af represent three variable resistancesor rheostats having total resistances of 2, 2 and 100 ohms respectivelyas indicated by the subjoined numerals. These rheostats are used torepresent the respective percentages of carbon, manganese and iron in aferrous alloy-in the present case an alloy which it is desired toproduce. The adjustment of the rheostats is such that 1 ohm represents1%-the settings indicated in Fig. 1 representing approximately 1% carbon15% manganese and 97.5% iron. Similarly the rheostats of the B, C and Dseries are adjusted to represent the respective percentages of carbon,manganese and iron in a remelting scrap, a pig iron and a ferromanganesealloy which, for the purpose of illustration, are considered availablefor compounding the desired alloy. It should be noted that the sum ofthe resistances in each of the four hori'zontl groups is made equal to100 ohms (representing 100% of the composition of each material).

The three rheostats of each horizontal group are connected in series and4 complete circuits are formed which (taking the A series as an example)comprise: Rheostat A0, con- 'ductor 1, rheostat Am, conductor 2,rheostat intensity of current is dependent upon the E. M. F. of thebattery and the resistance of the circuit. Furthermore if the availableresistance in rheostats I, J etc. is made several times that of thebalance of the circuits, the intensity of current in each circult willbe controllable within a considerable range by means of these rheostats.

To illustrate the principle of my invention I have elected to representpercentave by resistance, 1 ohm being arbitrarily chosen to represent1%. lIn like manner, milhampere of current in any of the horizontalcircuits is chosen to represent 10 pounds of the material to which thecircuit is assigned. For example, in the circuit containing rheostatsAc, Am and A, 1 milliampere Would represent 10 pounds of the alloy to beproduced, 1n the B circuit 10 pounds of remelting scrap, etc.

Bearing in mind that the sum of the resistances Ac-Am-Af, Bc-Bm-Bf etc.m each horizontal circuit has been made equal to 100 ohms, it Will beobvious that the total potential drops across the three rheostats in anyof the circuits are proportional to the currents flowing in the circuitsand that said potential drops may equally well be used to representweights of materials. F urthermore, the potential drop across anyindividual rheostat will represent the Weight of the element thepercentage of which the rheostat has been adjusted to represent. Forexample in the A circuit, in which A0 is set to represent 1% carbon (1ohm), Ava-15% manganese (1.5 ohms) and A 97.5% iron (97 .5 ohms), ifrheosat I is adjusted so that the current in the circuit is 100milliamperes (1000 pounds) the total potential drop across Ac, Am and Afwill be 100 .100=10 volts or 10,000 millivolts, and 10 millivolts W111therefore represent 1 pound of material.v

Taking the individual rheostats', the drop across Ac (1 ohm) will be1.100=.1 Volt or 100 millivolts (10 pounds of carbon),

' across Am 150 millivolts (15 pounds of manganese) and across Af 9750millivolts (975 pounds of iron).

In Fig. 1 it will be noted that closure of any one of the switches C8,M8 or F8 completes a Vertical circuit in which the four rheostatsrepresenting the weights of a given element are in series and in which agalvanometer N, O or P is included. Thus in the left hand or carboncircuit, starting with galvanometer N I have conductor 7, rheostat A0,conductor 8, switch C8, conductor 9, rheostat B0, conductor 10, switchC8, conductor 11, rheostat C0, conductor 12, switch C8, conductor 13,rheosta-t Do and return to N by means of conductor 14. k

Each of the four'horizontal or Weight circuits form branches to theVertical circuits such as that just traced and under ordinary conditionscurrents in the horizontal circuits Will divide in a highly complexmanner, a

portion of each flo'wing in the Vertical Circuit and other portions inthc adj acent horizontal circuits. However, since the purposc of theVertical circuits is to arrive at a particular condition of the eurrentsin the horizontal circuits, the mere fact that said complex currents areflowing and thereby causing deflection of the galvanometer in a.Vertical circuit gives us all the information needed.

' The obvious condition to be fulfilled in the solution of a chargecalculating problem is that the materials charged must cumulativelysupply the correct Weight of each of the elements required in thecharge; in other words,`

the sum of the weights of each element in the charged materials mustequal or balance the weight of said element in the required weight ofthe desired composition. Since, as pointed out above, I have representedthe Weight of each' element in each of the chargin g materials and inthe desired composite charge by the Voltage drop across a rheostat, thesolution of the problem requires that the sum of the Voltage dropsacross the elementrheostats of the materials circuits be made equal tothatacross the corresponding rheostats in the desired analysis circuit.The purpose of the respective Vertical or balan'cing circuits is toindicate when this equality has been attained with respect to theelements which they represent.

To this end, it will be noted that the polarity of the battery supplyingthe analysis desired oi' A circuit is reversed with respect to those ofthe ;other three (B, O and D) circuits. If, therefore, the sum of thepotential drops across rheostats B0, Cc and Do equals that across Ac(100 millivolts in the case assumed), no current will fiow in theVertical circuit when switch C8 is closed and the condition of balanceWill be indicated by lack of movement in galvanometer N. iThe process ofcalculation consists in so adjusting the currents in the three lowerhorizontal circuits by means of rheostats J, K and L that this balancedcondition is attained With respect to all (representing weights ofcharging materials) three elements. It should be notfd that tests forbalance must be made by closing only one of the switches C8, Ms and F8at a time, since theclosure of two switches simultaneously would providebranched cir-.

cuits in which the potential drops Would not be comparable.

When balance has been attained, the weights of the charging materialsmay be read from the milliammeters F, Gr and I-I, using the assignedConversion factor of milliamperes to units of weight.

It has been pointed out above that the total Weight of a furnaceaddition may be represented as well by the voltage drop across theseries of resistances which represent 100% of its composition as by thecurrentv producing said Voltage drop. This is equivalent to using theresistances (which are of equal Value for each furnace addition) asshunts in the well known method of measuring current. In order toeliminate the expense and complication of providing an ammeter for eachfurnace addition I have used this voltage drop method of currentmeasurement in t e commercial form of calculator illustrated in Fig. 2.In order to provide greater accuracy and to still further reduce thecomplexity of equipment, I use a potentiometer for measuring thesevoltages and employ a smgle galvanometer to balance the potentlometeragainst these voltages as Well as to balance the voltages representingsingle elements as in Fig. 1.

Fig. 2 shows a calculator for determimng the proportions of a maximum of4 ferrous materials for compounding a furnace charge. The chargeconsists of the four elements carbon, manganese, Silicon and iron. Itscomposition is represented by the series'of resistances headed by theletter A in which the rheostats C, Mn, Si and Fe may be set to representthe pro ortionate amounts of the elements denotedhy these symbols. Inlike manner series B, D and E represent the composition of threecharging materials or furnace additions. Series F consisting of only tworheostats, illustrates the use of a switching arrangement by means ofwhich a single rheostat may be used to represent any one of a luralityof elements (in this case either carh on, manganese or silicon) byproviding for its connection 'to the desired balancing circuit.

In order to extend the range of rheostat A-c without decreasing theaccuracy with which it may be adjusted, an auxiliary fixed resistance Qmay be inserted in the series by means of switch R. Resistance Qpreferably equals the total resistance of the rheostat so that, forexample, if each has a resistance of three ohms the range with switch Rin the left position will be 0 to 3 and, in the right position, 3 to 6.

P1 and P2 are potentiometers with scales calibrated in terms of weightand percentage. P1 preferably has a resistance ten times that of P2. Thetwo potentiometers are connectedv in series and current is supplied tothem from a dry cell thru the reversing switch L and the controlrheostat PR. Either P1 or P2 may be connected to the measuring circuitby means of the switch M.

Each Vertical series of percentage rheostats (A, B, D etc.) is providedwith a pair of control rheostats (Se and Sh) which regulate the currentthru the series. Rheostats Se are in series with the percentagerheostats and with the shunt rheostats, S71.. The latter complete returncircuits to the batteries and supply current to the percentage rheostatsby a potentiometer connection from their movable contacts. The series(A, B, D,

etc.) are separately supplied with current from individual dry cells (1,2, 3, 4 and- 5) o mit accurate setting of the rheostats (A0,

Amn-Bo, Bmn, etc.) by measuring potential drops across them incomparison with that across standard resistances Az, Bz, etc.Resistanees Az, Bz, etc. each has a resistance equalto the totalresistance of the rheostats 1n a slngle series when set to represent ofa material-normally 100 ohms. The rheostats may or may not be providedWith scales calibrated in terms of percenta e but in either caseaccuracy of settmg may e insured by this comparative method. Itsoperation is described below.

Switches Ay, By, etc. connect the terminals of their corre-spondingseries of rheostats to the potentiometer system whereby the voltage dropacross the series-representing the weight of the material inquestion-may be determined.

Switches S0, SMn, etc. when thrown to the right connect in series allrheostats representing a given chemical element and include in theseries a galvanometer connected thru terminals (ir-G. Thus, for example,when switch Sc is thrown to its right hand position, rheostats A-c, B-c,D- c, E-c

- and F-c (if switch K is in its left position) are connected in seriesand the circuit completed thru the galvanometer. The weight of carbon inthe required charge (voltage across A--c) may then be balanced with theweight of carbon supplied by the furnace additions (sum of the voltagesacross B-c', D c, E-c and F-c) by adjusting the various current controldials (Sh and Se) until no deflection of the galvanometer is obtained.

Switch ST connects the voltages across the whole of all groups A, B, D,etc. in series and completes a circuit thru the galvanometer so that thetotal weight of the furnace additions may be checked against the weightof the charge required.

Switch N is used for connecting either the standard resistanees Az, Bz,etc. or individual percentage rheostats Ac, BMn, etc. at will with thepotentiometer system in conjunction with switches Am, Ba), etc. and Sc,SMn,etc. as explained below.

In order to clarify the functionof each part I give below a Summary ofthe process of calculating a furnace charge:

Assume that it is desired to make 10001bs.

of steel of the following analysis, using the following materials:

Series Material Carbon ;31% Silicon Iron A Analysis requred 90 l. 3. 0095. 00 B Scrap steel .50 .20 .30 99.00 D Pig iron 3.50 .50 1.00 05.00 EFerromanganese 1. 00 40. 00 58. 50 F Ferrosilcon 80. 00 20. 00

materials, it should be noted that the choice' is .only restricted withrespect to the charge desired. The analysis of the charge desired mustalways be set up on series A since the battery connections of thisseries are reversed with respect to those of the other series. Thematerials used to make up the charge may be assigned to the variousother series provided in the instrument so as to most fully representtheir analyses. It may be necessary for example, to omit certain elementrheostats from some of the series for reasons of economy, or limitationsof space. Such short series should be used to represent the analyses ofmaterials containing only a few elements in comparatively largepercentages. The materials thus represented should also make up arclatively small part of the charge so that the ininor amoun-ts ofelements contained ther'ein which cannot be set up on the short seriesWill not seriously affect the final analysis of the charge.

An example illustra-ting' these points in the present case is furnishedby the assignment of ferrosilicon to series F which contains only twoelement rheostats. The ferro- Silicon used as an example is assumed tocontain only silicon and iron and is therefoz'e fully represented by thetwo rheostats of series F.

(2) Throw switch K to the right. This switch is included in thedescription and drawing to illustrate the possibility of using a singlerheostat to represent any one of a plurality of elements. By throwingswitch K to the right in the present case the top rheostat of series Fis made to represent silicon. The switch accomplishes this function bysetting up connections which (When switch Ss is closed) result in acomplete circuit including the rheostat as Well as the S rheostats ofthe A, B, D and E series and the galvanometer. A partial circuit Will bctraced herewith to show that this rheostat (F c-'mn-s) When switch K isin the right hand position, bears the same relation to switch Ss as theother Si rheostats. The tracing of the complete balancing circuit forsilicon will be deferred till later.

starting With rheostat D872 I have Wire 7, contact 8 of switch Sai,which makes contact with contact 9 When this switch is closed, Wire 10,Wire 11, rheostat ES, Wire 12, contact 13, contact 14, Wire 15, Wire 16,contact 17 of switch K which in the right hand positi on of this switchmakes contact With contact 51, Wire 19, rheostat F c-mn-sz', Wire 32,contact 37 of switch K, contact 38, Wire 39 and contact 40 of switchSsz'. The three rheostats D871, Es and F c-'mm-.s' are thus in seriesWhen switch K is in its `right hand position and switch Sm' is closed.

In like manner switch K places rheostat F c--mn-8 in series with themanganese and carbon rheostats when in its center and left handpositions r-espectively and when the Sm-n and Sc switches respectivelyare closed. 'The circuit for manganese is: rheostat Dmn, Wire 20,contact 21 of switch Smn, contact 22, Wire 23, Wire 12, Wire 24,rheostat Emn, Wire 25, contact 26 of switch Smn, contact 27, Wire 28,contact 29 of switch K, contact 30, Wire 31, wiz'e 19, rheostat F`c-mn-8, Wire 32, contact 33 of switch K, contact 34, Wire 35, contact36 of switch Sm'n.

It should be noted that switch K places rheostat F c-nm-sz' in one ofthree circuits (C, Mn or Si) and, at the same time closes the twocircuits in which the rheostat is not inserted. Taking the carboncircuit for example With the switch K in its center position as shown inthe drawings and by which the rheostat is'placed in the manganesecircuit I have: rheostat E0, Wire 41, Wire 42, contact 43 of switch Sc,contact 44, Wire 45, contact 46 of switch K, contact 47, Wire 48 andcontact 49 of switch Sc. The net effect is therefore to short circuitcontacts 43 and 49. VVith switch K in its right hand (Silicon) positioncontact is also maintained between contacts 46 and 47. Vith switch K inits left hand (carbon) position however contact is broken betweencontacts 46 and 47 and coming from contact 43 of switch Sc by means ofcontact 44, and Wire 45, I have contact 50, contact 51, Wire 19,rheostat F c-mn-8i, Wire 32, contact 52, contact 47 and return tocontact 49 o f switch Sc by Way of Wire 48. The rheostat F c-mns'i isthus placed in the carbon circuit.

In like nianner With switch K iu its left and (carbon) position, and inits center (manganese) position the silicon circuit is closed bycontacts and 38 which short circuit contacts 13 and 40 of switch Saithrough wires 15 and 39; and with switch K in its left hand (carbon) orright hand ('silicon) positions the inanganese circuit is closed bymeans of contacts 57 and 29 or 56 and 34 respectively through wires 28and 35.

(3) Set potentiometer P1 at 100% and ad- 1,888,oo9 l left, N to the leftand Am to the right. Adp just A80 and Ash until a balance is obtained'as indicated by zero deflection of the galvanoineter.

(4) Throw switch N to the rlght set P1 or P2 to the percentage of carbondes1red (1n this case 90%) close switch Sc and adjust rheostat Ac to abalance. Repeat for the other element rheostats (Am'n, Asi, etc.) usingthe corresponding switches (Smn, Ssz', etc.

Ags noted above these steps and. 4) in the procedure of calculation arefor the purpose of accurately adjusting the resistances of theindividual element rheostats to represent the percentages of theelements contained in the charge and the charging materials. If theelement rhcostats are calibrated with suflicient accuracy these Stepsmay be omitted but, since the available materials used in steel meltingOperations remain constant in composition over considerable periods oftime, it may provel equally convenient and more accurate to adjust therheostats by this method than to rely on a previous calibration. Most ofthe rheostats may of course be left in` the same adjustment from oneproblem to another.

The method used in adjusting the rheostats is based on comparing theVoltage drops across them with that across a known fixed resistance.carrying the same current. The voltage drops are measured by means ofone of the potentiometers P1 or P2. These are calibrated in terms ofpercentage so that the desired percentage may be set up on each rheostatby setting the potentiometer to this percentage in each case and thenadjusting the rheostat until a balance is obtained. The functions of thevarious electrical units will be illustrated by setting upthepercentagcs of elements in 'the charge which is given above, namelycarbon .90%. manganese 1.10%, Silicon 3.00% and iron 95.00%.

Switch L connects battery 6 to the potentiometers P1 and P2 as follows:battery 6, Wire 58, contact 59` contact 60, Wire 61, control rheostatP'r, Wire 62, potentiometer P2, Wire 63. potentiometer P1 Wire 64,contact 65, contact 66 and return to battery 6 by Wire 67. Switch L is'a reversing switch of usual design and in the above I have assumed itto be in its right hand closed position. If it at any time becomesnecessary to reverse the polarity of the potentiometers the switch maybe closed in its left hand position. Rheostat P'r is used to limit thevoltage drop across the potentiometers to a desired portion of thebattery voltage as per common practice. As before stated potentiometerP1 is conveniently of such total resistance and so calibrated as torepresent a maximum of 100%` and also a maximum weight which lshould becomfortably in excess of the maximum furnace charge which is to becomuted. P2 is conveniently made with one tenth the total resistance ofP1 and is calibrated to a maximum of 10% and a maximum Weight one tenthas great as P1.

Switch M connects either P1 or P2 to the balancing circuit When thrownto the left or right respectively. Switch N connects the potentiometersto the individual element rheostats or to the standard resistances (Az,B2, etc.) When in its right hand or left hand positions ,respectively.Switches Am, Bm, etc. connect the batteries 1, 2, 3, etc. to theirrespective Vertical series (A0, Amn; Bo, Bmn, etc.) When in either theirri ht hand or left hand positions. When in t eir'right hand positionsthey also .connect fixed resistances Az, B2, etc. in series`with theirrespective Vertical series of rheostats.

With M left, N left and Am right I have: end of Winding of potentiometerP1, Wire 64, contact 68 of switch M, contact 69, Wire 70, Wire 71,galvanometer at G-. Returning from the galvanometer at G'- I have Wire72, contact 73 of switch N, contact 74, Wire 75, contact 76 of switchAm, contact 77, wire 78, fixed resistance Az, wires 79, 81 and 80,contact 82 of switch Am, contact 83, Wire 84, contact 85 of switch N,contact 86, Wire 87,

contact 88 of switch M, contact 89 and Wire 90 to the arm .of.potentiometer P1. I thus have a circuit including aL segment ofpotentiometer P1, fixed resistance Az and the galvanometer. ,Thepotentiometer segment and resistance Az also form portions of othercircuits and the voltage drops across them may lbe opposed by properselection of polarlty brought to a balance (With potentiometer P1 set atby adjustment of the current "through either or both circuits.-

The other eircuit which includes Az is defined as follows: starting atthe right hand end of shunt rheostat or potentiometer A871., Wire 105,contact 96 of switch Am, contact 77, Wire 78, resistance A2, Wire 79,Wire 81, rheostat AFe, Wire 97, rheostat Asi, Wire 98, rheostat Amn,Wire 99, contact 101 of switch R, contact 100, Wire 102, rheostat Ac,Wire 103, Wire 104 and return to the arm of shunt by means of switch L,and may be rheostat Ash. This 'circuit is supplied With 'I-Iavingestablished a current through the element rheostats and fixed resistanceAz of such value that the drop across Az is equal to 100% on thepotentiometer scale I can ad]ust the drops across the individual elementrheostats to any desired part of 100% by balancing them against acorresponding setting of the potentiometer. In terms of percentage thisis equivalent to making the percentage of Azequal to 100%. When properlyadjusted, the sum of the resistances of the element rheostats (A0, A'mn,A82' and AFG) should equal the resistance of Az and hence 100%. In usingthis method it isof course essential that the current in the circuitincluding Az and the element rheostats should not change during thecomparison. If the element rheostats are previously adj usted toapproximately thelr correct resistances, the final adjustment Will notseriously effect the current in the circuit since the adjustmentsinvolve only slight changes in the total resistance of the circuit. Ifthe utmost accuracy is necessary however, the checking of Az may berepeated after the preliminary adjustments, followed by a second set ofadjustments of the element rheostats.

The circuit set up for balancing the individual element rheostats is'illustrated by the following in which rheostat A0 is used as anexample. Switch N is thrown from left to right, switch Am remains closedto the right and switch Sc is closed. Since the percentage of carbon islow it is convenient to use potentiometer P2 by throwing switch M to theright. Potentiometer P2 is first set at .90%.- 'Then, starting Withrheostat Ac I have wire 103 and contact 107 of switch Sc. As Will beshown later, When switch Sc is closed all the carbon rheostats Bc, Do,etc. are in series so the present circuit includes these rheostats andreturns to contact 49. From contact 49 I have contact 108, Wire 109,Wire 110, through the galvanometer from G- to G+, Wire 71 Wire 7 O,contact 69 of switch M, contact 111, Wire 112, Wire 63, potentiometerP2, Wire 113, contact 114 of switch M, contact 88, Wire 87, contact 115of switch N, contact 116, Wire 117, contact 118 of switchl Sc, contact119, Wire 120, Wire` 99 and return to rheostat A0V through switch R.

Although all the carbon rheostats (B0, Do, etc.) are included in theabove circuit in addition to the particular rheostat (A0) beingadjusted-the other rheostats do not introduce extraneous voltage intothe circuit since the various Vertical circuits in which they areincluded are opened at switches B, D, etc. The efi'ect of theirinclusion in the circuit is therefore only to increase its resistance.This is of no importance since only voltage is being measured-by a zerocurrent method.

The adjustment of the ot-her element rheostats in the A series iscarried out in a similar manner-the articular element rheostat to beadjusted being selected by the closure of the corresponding switch SMn,S-S, etc. with all other S switches open. The same applies to therheostats of the other Vertical series (B, D, etc.)--using the switchesBx, Dan, etc. to select the series.

(5) As a check on the adjustments of the rheostats in a given series,switch St may bc closed. This connects the potentiometer across theentire series and should give al balance at a potentiometer setting of100%. The F e rheostat of each series may be adjusted by the circuitthus established rather than by closure of SFe and adjustment to thespecified percentage of iron. By bringing the series to a balance at100% by adjustment of the Fe rheostat I absorb the cumulative errors ofadjustment of the other element rheostats in the adjustment of theformer. This is desirable since the percentage of iron is of littleimportance in relation to the percentage of the other elements of thecharge. The circuit established through the A series by the closure ofST is as follows: beginning at rheostat A Fe, I have Wire 81, Wire 121,contact 122 of switch ST, contact 123, Wire 117, contact 116 of switchN, contact115, Wire 87, contact 88 of switch M, contact 89, Wire 90,pbtentiometer P1 Wire 64, contact 68 of switch M, contact 69, Wire 70,wire 71, through galvanometer from G+ to G-, Wire 110, Wire 109, contact124 of switch ST, contact 125, Wire 126, Wire 127, Wire 32, rheostatFc-Mn--S, Wire 19, Wire 128, rheostat F Fe, Wire 129, Wire 130, contact131 of 'switch ST, contact 132, similarly through series E to contact135, contact 136, similarly through series D to` contact 142, etc-comingfinally from series B to contact 149, contact 150, Wire 151, Wire 103and return through series A to rheostat A Fe. It Will be noted that inthis circuit are included all the element rheostats in the instrumentbut that voltage is only introduced by the drop across series A. The'resistance introduced in this case is-considerable but the voltage tobe measured is also high so that the accuracy of balancing is of thesame order as that which obtains in the adjustment of the individualrheostats. It may be noted at this point that the circuit traced aboveserves as a test of practically the entire instrument for open circuits.This is an example of the ease With which faulty apparatus or wiring canbe detected in this calculator-an inherent characteristic of its design.

(6) lVith switch N to the right, all switches Am, Bx, etc., closed tothe left and all S switches open, set the potentiometer at the desiredWeight of charge (1000 pounds in the present case), close switch Ay andbalance by adjustment of rheostats ASe and ASt` These Operations resultin setting up a i voltage on the potentiometer which is representativeof 1000 pounds and in making the voltage across the A series equal to itand hence also representative of 1000 pounds.

At this point it should be noted that in the foregoing adjustments thevalues of current used in the various vertical circuits bore nonecessary relation to each other. .I Was concerned only in making theresistances of the rheostats in the various circuits proportional to thepercentages they Werechosen to represent. The necessary7 correlation ofresistances was obtained by referring to fixed resistances Az, B2, etc.(all of which are of equal resistance) as standards. In subsequentOperations, however, voltage drops across all element rheostats orseries of same must represent weight on a common basis. Hence theotentiometer current must remain constant and all voltage drops (andhence currents) must be adjusted using the potentiometer as a reference.w

Closure of switches Am, B`w, etc. in their left hand positions connectsthe batteries 1, 2, 3, etc. to their respective Vertical serlesexcluding therefrom lfiXed resistances Az, Ba, etc. The circuitestablished in series A for example is: vpositive of battery 1, W1re'91,contact 92 of switch Am, contact 152, Wire 94, series rheostat ASe, Wire105, shunt rheostat or potentiometer A871., and returnto battery 1 byWire 106. The branch c1rcu1t from Ash is: Wire 105, Wire 95, contact 153of switch Am, contact 82, Wire 80, Wire 81, rheostat AFe, Wire 97rheostat AS, Wire 98, rheostat Am'n, Wire 99, rheostat Ac and return toAsh by Wires 103 and 104.

In order to extend the range of rheostat A0 as mentioned above, thefixed resistance Q may be inserted in the circuit by throwing switch Rto the right. "In thiscase the c1rcuit becomes Wire 99, contact 154 .ofswitch R, contact 155, Wire 156, resistance Q and rheostat A0, insteadof as traced above in the eighth paragraph under steps (3) and (4).

The closure of switch A3/ sets up a circuit which may be traced asfollows: starting with rheostat AFe as one end of series A, I have Wire81, Wire 157, contact 158 of switch Ay, contact 159, Wire 160, Wire 87to switch M and the potentiometer, returning from switch M by Wire 70,Wire 71, through the galvanometer from G+ to G-, Wire 110, wire 161,contact 162 of switch Ay, contact 163 and return to the other end of theseries at rheostat A0 by Wire 103.

If a definite Weight of one or more materials is to be charged such asdiscard metal from previous heats of steel,'the Weights of suchadditions should next be set up on suitable series by the same processused in (6). In the present case I assume however that all the otherseries available (B, D, E and F) are to be used to re resent as yetindeterminate amounts of the our charging materials.

(8) With switch M remaining in the left hand osition, and all switchesclosed and With a y switches open, close S0 and balance by adj ustmentof rheostats Se and Sh in series B, D, E and F. Open Sc, close Smwl andrepeat' the balancing. Continue in the same manner with SSz', and SF cand repeat these Operations as often as is necessary to obtain a balancefor all elements. This is the essential step in the process ofcalculation which results in the actual solution of the simultaneousequations involved. The volt- ,age across each element rheostat in the Aseries (representing the required charge) is 1n thls'step made equal tothe sum of the voltages across the corresponding element rheostats inthe other series (representing the charging materials). The significanceof this in terms of Weight is that the Wei 'ht of each element requiredfor making up t e charge in supplied jointly by the available materials.Assuming that switch K is in its right hand position thus eliminatingrheostat Fc-Mn -S from the carbon circuit I may trace the carbon circuitas lfollows:

switch Sc Will of c'ourse be closed. Starting With rheostat Ac I haveWire 103, contact 107 of switch Sc, contact 164, Wire 165, Wire 145,rheostat B0, Wire 144, Wire 17 4, contact 166 of switch Sc, contact 167,Wire 168, Wire 20, Wire 188, rheostat Do, Wire 137, Wire 169,

contact 170, contact 171, Wire 172, Wire 25, Wire 175, rheostat E0, Wire41, Wire 42, contact 43, contact 44, Wire 45, contact 46, contact 47,Wire 48, contact`49, contact 108, Wire 109, Wire 110, throughgalvanometer from G to G+, Wire 71, contact 176 of switch N, contact116, Wire 117, contact 118 of switch Sc, contact 119, Wire 120 andreturn` to rheostat A0 by Wire 99.

All carbon rheostats are thus included in acircuit which is closedthrough the galvanometer. Each of the rheostats is also included in aseparate outside circuit provided with its oWn sourceof current. It Willalso be noted thatl the rheostats are all connected in the main circuitin the samedirection but that the battery supplying the rheostat A0 isreversed in polarity With respect to those supplying the others. Whenthe circuit is first closed the current in it Will naturally divide in acomplex manner, adding to or opposing the floW of currents in the branchcircuits. We are not 4concerned however With the manner in which itdivides but rather With the fact that a current does floW as indicatedbythe galvanomcter. By adjustment of the various Se and Sh rheostats wearrive at a condition in Whichno current flows in the circuit. In thiscondition it is obvious that the voltage drop across A0 is exactly equalto the sum of the opposing voltage drops across the other rheostats.

The balancing operation is essentially a trial and error process in thatthe ba-lancing of one element by adjustment of the series containing itsgreatest percentage may introduce excessive quantities of the otherelements contained in this series. For this reason it may be necessaryto repeat the balancing several timesthe amount of repetition and hencethe time required depending on the experience of the operator. Ingeneral, the tirst adjustment should be made in that series containingthe greatest percentage of a single element or in the seriesrepresenting the least complicated analysis. For example, in the case ofthe materials given above, I adjust the F (ferro-silicon) series first,the E (ferro-manganese) series second and so on. IVith al littlepractice it becomes possible to approach the balance of all elementswithout completely balancing any individual element and hence withoutgreatly exceeding the required amounts of any of the others.

(9) Then a balance for each element has been obtained as outlined above,a. check 011 the total balance (weight of charge against weight ofcharging materials) may be obtained by closing switch ST.` This placesall the series of element rheostats in a single circuit with the Voltageacross the entire A Circuit opposed by the sum of the voltages acrossthe other circuits. The essential parts of the circuit thus establishedhave been traced under step (10) Throw switch N to the right and withall S switches open and w switches closed, close switch By and balancewith potentiometer P1 or P2. reading the potentiometer when balance isobtained in terms of weight. Repeat this operation by closing switchesDy, E3/ and F2/ one at a time. The weights read on the potentiometershould be the weights of the respective charging materials.

Taking series B as an example, the circuit set up in this' step by theclosure of switch By is as follows: starting with rheostat BFe as oneterminal of series B, I have Wire 148, wire 177. contact 178 of switchBy, contact 179` wire 161, Wire 110, through galvanometer from G-' toG+, Wire 71, wire to potentiometer P1 or P2. returning frompotentiometer by Wire 87, Wire 160, contact 180 of switch By, contact181, Wire 144 to rheostat Bo which is the other terminal of series B. Inthis circuit I have the voltage drop across series B opposed by thepotentiometer drop. The current in series B has been so adjusted in step8 that the voltage drop across the series represents the Weight ofmaterial (in this case scrap steel) which, together with the otheravailable materials, is required to make up the charge. This voltage isread on the potentiometer in terms of Weight.

I have illustrated above the calculation of the materials required toproduce a given weight of a given analysis. It Will be obvious that theapparatus can equally welll be used for the solution of the much simplertype of problem in which the Weights of'i;

number of materials of given analysis are given and it is required tofind the analysis and Weight of the resulting mixture. In this case thetotal weight of mixture is first determined by adjustment of A-Se andA-Sh in conjunction with ST and the analysis then found by adjustment ofthe individual rheostats in the A series in connection With theircorresponding S switches. Changes in total resistance of the A seriesdue to individual rheostat adjustments'must be taken care of byrepetition as above.

Solution of the problem given above by means of simultaneous equations(and using a slide rule) requires at least 15 minutes by one of ordinarymathematical abilit-y. With only limited experience the same Work can bedone by means of the calculator in from seven to eight minutes. The timerequired for more complex problems increases about linearly with theincreasing number of elements and furnace additions When the calculatoris used; While in the case of mathematical solution of simultaneousequations. the time increases at least as the square of the number. Thelatter is also approximately true of the methods of approximationheretofore used in calculating charges.

Having thus described my invention What I claim as new and desiretosecure by Letters Patent is:

1. In a calculating device, variable means for establishinginterdependent values of resistance, current and potential in electriccircuits, means for adjusting said values in terms of numericalquantities to be treated mathematically and means for evaluating theresults of interaction of said values in terms of said quantities.

2. In a calculating device, an element having an electrical resistancebearing a known relation to a numerical quantity, means for passingthrough said element current the intensity of which bears a knownrelation to a second numerical quantity, and means for determining theelectrical potential drop across said resistance in terms of a thirdnumerical quantity.

3. In a calculating device, a variable elec- 1 trical resistance, meansfor adjusting said resistance in terms of a numerical quantity, meansfor connecting said resistance to a source of current, means independentof said resistance for controlling the intensity of current through saidresistance, means for measuring said intensity in terms of a secondnumerical quantity, and means for determining the potential drop acrosssaid re- 1,8o8,ooo

sistance in terms of a third numerical terms of percentage, means forsupplying quantity.

4. In a calculatmg devlce, two or more vanable reslstances ad] ustable mterms of numerical quantities, means for supplymg electr1c currents tosaid resistances, means for controlhng sald currents, means for measurmgsaid ourrents 1n terms of other numerical antities, means for measuringthe potential ops across said resistances in terms of other numericalquantities and/or for balancing any one of said potential drops or thesum I of any number of said potential drops against any other one or sumof said potential drops.

5. In a calculating device, a plurality of variable resistancesadjustable in terms Vof numerical quantities and'connected in series,means for connecting said resistances to a source of electric current,means independent of said resistances for adjusting the intensity ofcurrent through said resistances in terms of a numerical factor, andmeans for determining the potential drops across said variablereslstances in terms of other numerical quantities.

6. In a calculating device, means for representing vcompound numericalfactors con- 'sisting of series of variable resistances each of saidresistances being capable of adjustment to represent a term of one ofsaid compound factors, means indenendent of said resistances forcontrolling the current through each of said series in terms of anumerical factor, means Afor measuring the potential drop across any ofsaid resistances in each of said series in' terms of numericalquantites, and means for balancing the otential drop across anyresistance in one o said series against the potential drop across anyresistance in any' other of 'said series or against the sum of thepotential drops across corresponding resistances in a plurality ofothers of said series.

7. In a calculating device, means for representin compound numericalfactors consisting o series of variable resistances, means for supplyingelectric current to sa'id series, means mdependent of said resistancesfor controlling the current through each of said series, means formeasuring the 'potential drop across any of said resistances in terms ofnumerical uantities, means for measurthe potentlal drop across any ofsaid seri s in 'terms of other numerical quantities,V

means for measuring the potential drop" i across any of said resistancesin terms of numerical quantities, and means for balancing the potentialdrop across any of said resistances in one of said series or the sum ofthe potential drops across corresponding resistances 1n a lurality ofsaid series against the 'potential rop across the correspondingreslstance in another of said series or against the sum of the potentialdrops across correspondlng resistances in a plurality of other series.

9. In a calculating device, a plurality of series of variableresistances, means for supplying electric current to said series, meansfor individually controlling the intensity of Current in each of saidseries, means for measuring the potential drop across said resistancesin terms of percentage, means for measuring the potential drop acrosssaid series in terms of numericalquantities, and means for balancing thepotential drop across any of,

said resistances in one of said series or the sum of the potential dropsacross the corresponding resistances in a plurality of said seriesagainst the potential drop across the corresponding resistance inanother of said series or against the`v sum of the potential dropsacross corresponding resistances' in a plurality of other series.

10. In a calculating device, a lurality of rheostats adjustable in'terms o numerical uantities, a plurality of current control r eostats, apotentiometer calibrated in terms of numerical quantities, a pluralityof sources of electric current, a galvanometer, conduc- 'tors connectingsaid rheostats in a plurality of series, conductors connecting one ormore of said control rheostats in series and/or shunt with each of saidseries, variable means for connecting said series to 'said sources ofelectric current, the vpolarity of one or more of said sources when soconnected being reversed with respect to that of the others, variablemeans for.co`nnecting the terminals of said series exclusive of saidcontrol rheostats to said potentiometer and galvanometer to form acomplete series circuit therewith, and means for connecting in seriescorrespondingly designated rheostats in a plurality of said series an'dfor completing an electric c'ircuit therewith through said galvanometerfor the purposes above set forth.

11. In a calculating device, a plurality of rheostatsadjustable in termsof numerical quantities, a plurality of current control rheostats, aotentiometer calibrated in terms of numerica quantities, a plurality ofsources of electric current, a galvanometer, conduc- 10 1,898',ooe

tors connecting said rheostats in a plurality of series, conductorsconnecting one or more of said control rheostats in series and/or shuntwith each of said series,'variable means for connecting said series tosaid sources of electric current, variable means for connecting theterminals of said series exclusive of said control rheostats to saidpotentiometer and alvanometer to form a complete series Circuittherewith, and means for connecting in series correspondingly designatedrheostats in alplurality of said series and for completing an electriccircuit therewith through said galvanometer in which a fiow of electriccurrent is opposed in direction to the potential drop across therheostats of one or more of said series included therein.

12. In a device for calculating furnace charges, a plurality of seriesof variable resistances, the individual members of which are calibratedin terms of percentages of chemical elements, means for supplyingelectric current to each of said series and for adjusting same in termsof quantities .of the chargino' materials or of the chargedesired, meansfor measuring the potential drops across said variable resistances interms of quantities of chemical elements, andmeans for balancing thepotential drop across any of.said resistances in one of said series orthe sum of the potential drops across the resistances representing thesame element in a plurality of said series against the potential dropacross the resistance representing the same element in another of saidseries or the sum of the potential drops across the resistancesrepresenting the same element in a plurality of other series.

13. In a calculating device, electric circuits 40 containing means forrepresenting numerical quantities by values of resistance current andpotential'proportional to said quantities, connecting means forproducing interaction of said values in accordance with the desiredmathematical Operations upon the quantities represented thereby andelectrical measuring means for evaluating the results of saidinteraction in terms lof said quantities.

In testimony whereof I hereunto aflix my signature.

CLEMSON H. WARD.

